Various embodiments of consumer-operated coin counting kiosks are disclosed in, for example: U.S. Pat. Nos. 5,620,079, 6,494,776, 7,520,374, 7,584,869, 7,653,599, 7,748,619, 7,815,071, 7,865,432, 8,024,272; and in U.S. patent application Ser. Nos. 12/806,531, 61/364,360, 61/409,050, 13/681,047, and 13/691,047; each of which is incorporated herein in its entirety by reference.
Many consumer-operated kiosks, vending machines, and other commercial sales/service/rental machines discriminate between different coin denominations based on the size, weight and/or electromagnetic properties of metal alloys in the coin. With some known technologies, a coin can be routed through an oscillating electromagnetic field that interacts with the coin. As the coin passes through the electromagnetic field, coin properties are sensed, such as changes in inductance (from which the diameter of the coin can be derived) or the quality factor related to the amount of energy dissipated (from which the conductivity/metallurgy of the coin can be obtained). An example of a property is the minimum value of the sensor signal as the coin passes through the electromagnetic field of the sensor. The results of the interaction between the coin and the sensor can be collected and compared against the properties of known coins to determine the denomination of the coin.
In some markets, however, different coin denominations have similar size and conductivity/metallurgy, especially when several countries gravitate to the same market. Such coins may cause similar sensor signals, including a similar minimum value of the sensor signal, making coin discrimination difficult and generating losses for the operator of the machine. For example, erroneously discriminating a lower value coin (i.e., an impostor coin) as a higher value coin (i.e., a valued coin) generates a loss equal to the difference between the nominal values of the coins. This discrimination error is known as a spoof. On the other hand, an erroneous rejection of a valid coin is a loss of profit that could have been collected by accepting the coin, also known as a forfeit. Accordingly, it would be advantageous to provide robust coin discrimination systems and methods that would work reliably for coins having similar size and conductivity/metallurgy.